I'm in my freshman year of high school too
I think that it can't hurt to talk to some of your teachers, maybe the ones that you like or trust the most. There were several instances last year when I had so much going on in life and I was so stressed about studying and completing assignments that I finally went to my teacher and explained everything, and each time they gave me an extension. However, I only tried this with the teachers I knew well and who I knew liked me, and there were definitely some teachers who wouldn't have given me an extension on something if my house burned down the day before it was due. I think you can sometimes just "tell" instinctively whether or not a teacher will be more lenient, although occasionally they will surprise you
If you talk to some of your teachers about what's going on and they can't give you more time to work on assignments (keep in mind, sometimes they just can't), then if they're good teachers they will at least be more understanding if you have to turn something in late or if it isn't your best work. They may also offer to help you before or after school, which can work wonders if you let them, trust me. So either way, it can't hurt to at least tell them your situation (at least the ones you trust).
And B's really aren't that bad, especially since you're so close to getting an A. If you work hard and get the help you need, I bet you could have A's by the end of the year. There's still plenty of time left for improvement.
Good luck!